Atomic layer deposition of Zn(O,S) thin films with tunable electrical properties by oxygen annealing

Abstract

Zinc oxysulfide, Zn(O,S), films grown by atomic layer deposition (ALD) were annealed in oxygen to adjust the carrier concentration. The electron carrier concentration of Zn(O,S) can be reduced by several orders of magnitude from 10 19 to 10 15 cm -3 by post-deposition annealing in oxygen at temperatures from 200°C to 290°C. In the case of Zn(O,S) with S/Zn = 0.37, despite the considerable change in the electron carrier concentration, the bandgap energy decreased by onlỹ 0.1 eV, and the crystallinity did not change much after annealing. The oxygen/zinc ratio increased by 0.05 after annealing, but the stoichiometry remained uniform throughout the film.

Temperature effect on zinc oxysulfide-Zn(O,S) films synthesized by atomic layer deposition for Cu(In,Ga)Se2 solar cells

“…10 2 X cm). 17,18,24,33 In the high temperature region, the carrier concentration lowering can be explained by the higher sulfur content of the Zn(O,S) films. Indeed, we can assume that the oxygen vacancies are replaced by sulfur atoms, which reduced donor defects and therefore the n-type carrier concentration of Zn(O,S).…”

“…The charge carrier concentration of Zn(O,S) films varies in the range of 10 15 À 10 19 cm À3 depending on the deposition temperature and the film composition. 17,24,33 For instance, Park et al measured charge carrier concentrations up to 10 19 cm À3 for Zn(O,S) films synthesized at the deposition temperature of 120 C. 23 Sanders and Kitai also measured values up to 1:7 Â 10 19 cm À3 but at 300 C. 17 Otherwise, the resistivities of the ALD-Zn(O,S) films usually evolve from those of ZnO (10 À3 X cm) to reach high values (! 10 2 X cm).…”

“…24,25,31,42 These modifications are mainly due to the nature and the concentration of the defects in the bulk crystal. These defects come from O vacancies, In the lower temperature region, the significant n-type carrier concentration increase is probably due to the increase of oxygen vacancies in the films.…”

“…ALD of Zn(O,S) has been widely studied in the literature, [17][18][19][20][21][22] and in general, special efforts are made on the film atomic composition control, in order to adjust the band alignment at absorber/buffer interface in CIGS solar cells and obtain high efficiency devices. In most cases, the authors demonstrated the existence of an ideal atomic composition by tuning the H 2 S=ðH 2 O þ H 2 SÞ pulse ratio in the temperature range of 120-125 C. [18][19][20][21][22] Few studies report the influence of sulfur annealing on ZnO, 24 and oxygen annealing on ZnS. 23 But, to the best of our knowledge, no detailed study has been reported on the effect of the deposition temperature on Zn(O,S).…”

Tunable Electrical Properties of Vanadium Oxide by Hydrogen-Plasma-Treated Atomic Layer Deposition

“…The material properties of thin films grown by conventional thermal ALD and plasma-enhanced ALD (PEALD) are generally varied by controlling the deposition parameters, such as the growth temperature, precursor dosing and purging conditions; postannealing conditions; and extrinsic doping/alloying. 22−25 An alternative approach is to alter the conventional ALD sequence by incorporating additional reactive plasma/metal precursor steps into the growth cycle, which has been shown to modify the electrical properties of ALD-grown ZnO thin films. 26…”